As far as Neapolitan pizzas and gelato, you cannot go wrong with Mercurio's! I am actually shocked that I have not reviewed this yet... I really thought that I did.
We come here about once a week, and have never had a bad experience. I cannot say that I stray too far out of my comfort zone though in terms of what I order. I always seem to get the Insalata Della Casa and a Margherita pizza (if I do stray, I go with the simple Marinara pizza). Their gelato is some of the best that I have ever had... especially the Samoa flavored one, or the coconut cream. In a word... YUM.
The service is always fast and pleasant too. The have some wines and beers as well if you would like to enjoy a beverage with your meal.
I highly recommend checking it out if you have not been here. It has become one of my top favorite pizzas in Pittsburgh.